The present invention relates to an apparatus and process for measuring the filtration efficiency of a moving air-permeable web. It is particularly useful in the manufacture and processing of filter media.
In the prior art, the filtration efficiency of a media is done on stationary samples of the media after the manufacturing process is completed. If the media fails to meet design specifications, an entire lot of media from a particular manufacturing run may have to be discarded. The prior art has not provided for an on-line filtration efficiency test system whereby filtration performance can be measured continuously on a moving web as the media is being made or processed. There has been a need for such a system, because it would allow immediate corrective action and control of the media manufacturing process. The prior art test systems incorporate a sampling head that seals with the media. To use such an apparatus on-line would require that the moving web be stopped. This is not a viable solution to the problem of obtaining efficiency measurements on-line during the manufacturing process.
The present invention solves these problems associated with the prior art by providing a flow distributing and non-sealing sampling head positioned about the moving air-permeable web. It has been found that the present invention provides for accurate filtration efficiency measurements on the moving web during the manufacturing process, allowing for continuous monitoring of the web to ensure that the web being produced meets design specifications. If the filtration efficiency falls outside of the design specifications during the on-line testing, immediate corrective action can be taken.